The Conspirator: Redford Helms Another Dull History Lesson.

Set in the months after Lee's surrender at Appomattox, The Conspirator follows the consequences of the fatal shot at Ford's Theater—specifically, the trial of Mary Surratt, Catholic, 42, and the owner of a Washington, D.C., boarding house, who was presented before a military tribunal as the den mother in the conspiracy to assassinate President Lincoln.

Robin Wright plays Surratt, but, seen through the limited vantage of her defense, she's not the film's star. Maryland Senator Reverdy Johnson (Tom Wilkinson) decides that no Southerner can represent Surratt without compromising the case, so he hands her over to Union Army vet Frederick Aiken (James McAvoy). All of 28 and vainly trying to pass as older under a sparse, reddish beard, dubious ex-blue-belly Aiken becomes convinced that Surratt's trial is nothing short of a railroading.

Square-jawed and knotty-fingered, Wright fits her part and period, but McAvoy's Aiken is the one who carries, and stumbles with, the film. Aiken is chosen to represent Surratt in part for his wartime credentials—he's introduced bleeding on a History Channel battlefield—but nothing in McAvoy's pushover peevishness suggests knowledge of command or the burdensome memory of war. This would matter little if there was any transference from Surratt, if Aiken absorbed her toughness through their partnership, but such gravitas never arrives. The story is one of idealistic youth speaking truth to power, with Kevin Kline's Secretary of War Edwin Stanton the archetypal cynical insider, but after Aiken's closing argument, you're mostly stirred to watch Danny Huston's prosecuting attorney break him.

Showing a government system as it responds to an attack, The Conspirator is Robert Redford's first film since the awful—and similarly themed—Lions for Lambs (2007). Redford, never the subtlest of dialectic filmmakers, has now become the browbeating professor he played in Lions.

His latest lecture is the debut production of the American Film Company (motto: "Witness History"), created by Chicago entrepreneur and Cubs owner Joe Ricketts to bring our past accurately to the screen—an endeavor that, on paper at least, sounds worthy. Since Raoul Walsh's John Wilkes Booth blew flash powder down Lincoln's collar in Birth of a Nation, the events surrounding the Lincoln assassination have been dramatized surprisingly infrequently: Virginia Gregg played Surratt in an Ida Lupino-directed episode of The Joseph Cotten Show from 1956, while John Ford attempted a posthumous exoneration of Dr. Samuel Mudd, the Maryland doctor accused of conspiracy after setting Booth's broken leg, in The Prisoner of Shark Island (1936).

The Conspirator, though, fails to blow dust off its period. The historically obscure figure of Aiken is hardly vivified. Courtroom scenes are stagey, with cued-up gasps and canned laughter. Redford shows some flair with assassinations and executions, but the most done to enliven the dialogue is having Aiken and Johnson talk while the latter is using the bathroom. After the first reel, there's rarely any sense of a larger polis outside the museum-room interiors. The film is a burdensome two hours, even as some scenes seem to have gone missing, like the brushed-past plot point with Shea Whigham as a witness for the defense suborned by the prosecution, wasted along with Alexis Bledel and Evan Rachel Wood.

Convicted through, essentially, a single testimony, Surratt was hanged with three others in July 1865. There is a famous photo in which you can see her swinging to their left, bound up in a black dress. Mary Surratt and Sam Mudd were both, perhaps, innocent—this is beyond movies to prove. But Redford's dudgeon and bludgeon is a mere classroom aide next to Ford's mythical-historical consciousness and redemptive rawness or—to seek a less canonical comparison just down the multiplex hall—next to the workmanlike plotting and fizz of The Lincoln Lawyer. Barely worth the extra credit, kids.